fix(mobile): stop membership provider re-querying on session changes

[UgaTheDev]

Problem

communityMembershipProvider issues a fresh POST /query far more often than it needs to, showing up as /query bursts and aborted in-flight requests in the relay access log (#7734).

Mechanism

mobile/lib/shared/community/community_membership_provider.dart:107-113. Two things compound:

1. The provider is FutureProvider.autoDispose with no keepAlive(), so it is torn down whenever its last consumer (person_invite_section.dart, invite_create_provider.dart, currentCommunityRoleProvider) unmounts, and the next mount re-runs the body and re-queries. This is the half the regression test reproduces on main.
2. It ref.watches relaySessionProvider.notifier, which makes it a dependent of the session notifier element, so any RelaySessionNotifier.build() re-run (it watches relayConfigProvider, authProvider, ageSignalProvider) rebuilds this provider too. This half is by code reading: on Riverpod 3.1 a raw state = emission does not propagate through .notifier, so the "session state changes" test in this PR passes on main as well; the dependency bites on build() re-runs (auth / config / age-gate changes), which the test fake does not exercise.

The sibling channelMembersProvider (channel_management_provider.dart:512) already avoids both: it ref.reads the notifier and uses ref.listen(relaySessionProvider, ...) to invalidateSelf() only on a transition into connected. This provider never got the same treatment.

Fix

Mirror the sibling's session handling: ref.read instead of ref.watch on the notifier, and an explicit ref.listen that refetches only when the session transitions into connected. For the remount half, ref.keepAlive() rather than the sibling's snapshot cache — simpler, same effect for a single-instance provider. Community switches still invalidate via the existing ref.watch(relayConfigProvider), and the explicit ref.invalidate(communityMembershipProvider) retry paths (invite_create_page.dart, person_invite_section.dart) are unchanged.

Membership is still enforced by the relay (VISION.md: "The relay enforces all access control"), so a snapshot that is stale until the next reconnect or explicit retry has the same staleness window channel members already accept.

Test

mobile/test/shared/community/community_membership_provider_test.dart — new communityMembershipProvider caching group with a counting RelaySessionNotifier fake:

• no re-query on reconnecting / disconnected transitions (passes on main too, see above)
• no re-query on consumer remount — fails on main: Expected: <1> Actual: <2>
• re-query on explicit invalidation and on reconnect — fails on main: Expected: <3> Actual: <2> (the reconnect refetch is new behavior, matching the sibling)

Run locally with the Hermit-pinned Flutter: flutter test 6/6 on this branch; dart format --set-exit-if-changed clean; flutter analyze clean.

Duplicates

None found (is:pr is:open 7734 in:body → 0).

Out of scope, same anti-pattern, worth a follow-up: pulse_provider.dart and forum_provider.dart also ref.watch(relaySessionProvider.notifier).

Fixes #7734

🤖 Generated with Claude Code

https://claude.ai/code/session_01Qnxf2u2kSBxRM1AT7kD8BD

[github-actions]

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